The class of thermoplastic polymers is well known in the art, in part because of the property inhibited by many thermoplastics of being deformable at relatively low temperatures. Such thermoplastics are processed by conventional techniques such as extrusion or injection molding into sheets, films, fibers and molded articles of established utility. However, the low temperature deformation that makes many thermoplastics useful serves to preclude their usage as engineering plastics in applications where elevated temperature is likely to be encountered.
In order to increase the melting point or glass transition temperature of a thermoplastic, it is often useful to include the presence of multiple ring systems within the polymer chain. The rings of such a cyclic system are frequently connected by linking groups such as keto, oxy and sulfonyl. One class of these polycyclic thermoplastic polymers is designated by the term polyetherketone because of the presence within the polymer chain of aromatic rings connected by ether, i.e., oxo, linkages as well as by keto groups. Rose et al, U.S. Pat. No. 4,320,224, describe polymers having repeating units of formula ##STR1## employed alone or in combination with other similar repeating units. A commercial polyetherketone of this type, marketed by Imperial Chemical Industries, Ltd., under the tradename Victrex Polyketone has a glass transition temperature on the order of 150.degree. C. It would be of advantage to provide a class of polyetherketones of even higher glass transition temperatures.